The only difference I have with your statement is that I do have some sympathy with the fired engineer. He naively thought that there would be no consequence for speaking freely, and, even worse, that his work would have some impact at Google. Life lessons are sometimes hard.

Actually it's easy to create a targeted survey sent to one or a few selected individuals but ostensibly randomly distributed.

The effort is to get the unsuspecting, suspected employees to be on record with their unPC opinions and make a firing easier to stick.

Also, "anonymous" company surveys are not really anonymous. Companies are not interested in what you have to say. Keep your head down and don't complain about anything, even your salary or hourly rate. If you're not making enough money, try to find another job.